Studies are undertaken to elucidate the mechanisms underlying synaptic transmission in the vertebrate retina. Intracellular recording techniques are used primarily, in lower vertebrates, mainly salamander. The electrical changes in cellular activity, potential conductance, and reversal potential measurements in each cell-type establish the effects of the endogenous synaptic transmitters on postsynaptic cells. Then pharmacological intervention is used to isolate and characterize specific synaptic pathways. At present we have been able to characterize the electrical effects of separate synaptic inputs to each cell type. We propose to continue these studies, using putative transmitter agonists and antagonists to build a detailed picture of synaptic mechanisms in the retina.